Make Blintz Crepe:
Combine 1 cup flour, 1-1/2 cups water, 3 eggs, pinch of salt until smooth. Add more water if too thick. If you let it sit a few minutes, it is easier to stir, so there are no lumps.

Heat a bit of oil in a frying pan. Pour a thin layer of the flour mixture into the frying pan. Careful not to make the crepe too thick. It takes a little practice to get this right. When the blintz starts to leave the sides of the pan, flip it or turn it over carefully, Fry on the second side for just a few seconds.

Once all the crepes are cool, fill with a tablespoon of mushroom filling and wrap up into a blintz by turning in two sides and rolling up the rest.

Make Filling:
Sauté onions in 3 tablespoons of margarine until transparent.